6 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.79 



are thick shelled and tough. The genus is peculiar in that it passes 

 the winter in the egg stage rather than the adult, as is usually the 

 case in the Chrysomelidae. The fragile, thin integument of the 

 adult is ill fitted to weather the snows of winter or the parching 

 droughts of arid regions, particularly in the northern climates, which 

 THrhabda as a rule inhabits. 



Although the larvae of T. canadensis are conspicuous in their 

 glistening blackness on the tops of goldenrod, they do not compare 

 with the brilliant metallic-lustrous larvae of T. hacharidis or of some 

 of the western species. A detailed description of the larva of cana- 

 densis and notes on other species are given in Dr. Adam G. Boving's 

 paper on Beetle Larvae of the Subfamily Galerucinae." 



The larvae go into the ground just below the surface, where they 

 form cases in which to pupate. The pupal stage lasts a week or 

 two, evidently depending somewhat on climatic conditions. The 

 height of the season of adults is late in June or in July in the 

 latitudes of Washington, D. C, and Los Angeles and San Francisco, 

 Calif. In Massachusetts, adults of virgata occur in numbers in 

 August, and in the Yellowstone National Park I took adults of 

 three species, two in abundance, early in September. Early in June 

 at the Grand Canyon, Ariz., I found nearly mature larvae of 

 another species. One generation a year is apparently the rule. 



As far as known, the larvae remain feeding on the tender foliage 

 of their food plant. In T. hrevicoUis^ in this paper referred to an- 

 other genus (see p. 33), a different habit is recorded by J. D. 

 Mitchell, who writes, "The larvae burrow into the ground where 

 it is slightly raised, making runs or galleries, from which they crawl 

 out and about day and night, but never more than a few inches from 

 the colony home." ^ 



GEOGRAPHIC DISTRIBUTION AND VARIATION 



The genus as a whole belongs to the Transition and Boreal Zones. 

 In most species the food plant is a composite, particularly goldenrod 

 {Solidago) in the East and sagebrush {Artemisia) in the arid coun- 

 try of the West. The eastern species are few and not very vari- 

 able in markings. Of the six species known to occur in the Eastern 

 States, canadensis, hacharidis, and virgata are most common. Both 

 canadensis and virgata feed on goldenrod, and occur from Canada 

 southward, but are increasingly scarce south of New Jersey. T. hach- 

 aridis feeds on the salt-marsh composite Baccharis, which occurs on 

 the coast all the way from southeastern Massachusetts to the Gulf 

 of Mexico. T. canadensis and T. virgata extend across the northern 



• Proc. U. S. Nat. Mus., vol. 75, art. 2, pp. 1-48, 1929. 



' Chittenden, F. H., U. S. Dept. Agr., Div. Ent. Bull. 38, n. s., p. 108, 1902. 



